Field
Exemplary embodiments relate to a method using vapor liquid solid (VLS) for the synthesis of nanostructures for an electroluminescent source. More particularly, exemplary embodiments relate to the synthesis of tin (Sn) self doped Zinc Sulfide (ZnS) nanostructures for electroluminescent white light source.
Discussion of the Background
White light is produced by combining, in a proper combination, three basic colors, i.e., red (R), green (G), and blue (B). Based on the proportional weight of red or blue, the light source can be labeled as warm or cool. Presently, there are two ways of producing white light, by having three LEDs (RGB) as three sources of colors and using blue LED and two phosphor coated materials. Both techniques have their advantages and disadvantages. Economic cost is a large issue related to white light sources. So far, enormous efforts are being made to develop either technology or fabricate a material that can produce white light at low cost.
ZnS is a wide band gap material with an energy gap of 3.7 electron volt (eV). Crystal structures of ZnS can have two major structural defects, i.e., Zn vacancies and S vacancies. The two vacancies lead to formation of defect energy states in the band gap that are highly luminescent. S vacancies lead to emission blue color at 440 nm and Zn vacancies lead to emission of green wavelength at 520 nm, which are well established in the art. Due to the dominance of Zn vacancies, ZnS is being used as green phosphor material or green electroluminescence material. However, if ZnS is doped with either Au, Mn, Ga or Sn. A third low energy band may be introduced into the band gap, which may lead to emission of red wavelength light, i.e., in 600-650 nm range. The amount of Zn and S vacancies has been reported to depend strongly on the choice of catalysts, growth, and post growth processing conditions. Incorporation of metal ions may provide an efficient radiative channel by introducing defect states in the middle of band gap. Introduction of extrinsic defects also alter the balance of various optically active states participating in the recombination processes and thus substantially modify the radiative recombination channels and kinetics in the host material. Thus, the choice and location of the metal ion in the host lattice is very important for defining the radiative recombination pathways.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the inventive concept, and, therefore, it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.